cocos2d for iPhone

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1. 

   Omegas7
   Member

   All this time I never paid much attention to memory management, but it is time to take a deeper look at it.

   In Cocoa Dev Central, I found this setter method:
   

   - (void) setPhotographer: (NSString*)input
   {
       [photographer autorelease];
       photographer = [input retain];
   }

   I think I understand why we write [input retain], but why [photographer autorelease];?
   I see, autorelease will, well, release the object "soon", and I can be sure that the object will remain intact until the end of the function. But, why release photographer? I am going to set it a different value in this function (input), no? I mean, I release things that I won't be using anymore, right? Why would I release/autorelease photographer if I am still going to use it?

   This might be quite a newbie question, I fear this stuff of memory management was never my favorite concept in Objective-C..

   Posted 1 year ago #
2. 

   Novvy
   Member

   When you release something you are giving up a reference to the object. When memory is cleaned up it is exactly that: MEMORY being cleaned up. Pointers are not the data stored in memory themselves, they are a way to "name" a particular location in memory where the data is.

   In your supplied example we release the hold we have on the object that "photographer" is pointing to. We retain "input" as we want to keep the object stored there within memory (ie, stop it from being cleaned up) - which photographer is NOW pointing to.

   Consider this:

   [photographer autorelease];
   photographer = input;
   [photographer retain];

   Posted 1 year ago #
3. 

   TBBle
   Moderator

   You release photographer because presumably that object reference was stored there by this same method previously. And it retained it then, when it was input. And if you retain something, you must release it.

   The other reason to autorelease rather than just release is the case that input == photographer. Compare that to:

   - (void) setPhotographer: (NSString*)input {
    [photographer release];
    photographer = [input retain];
   }

   By-the-by, note that this is the canonical example of an synthesised "retain" setter.

   Posted 1 year ago #

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